SMTP (Mail)
SMTP stand for Simple Message Transfer Protocol. Mail message is sent by using this SMTP protocol. The mail message is relayed by some SMTP server.
Almost message is relayed normally and is sent to others. but seldom times, the message is not sent by any reason. SMTP status code is useful for investigating the reason why their message is not able to send normally.
- SMTP Status Code
| 250 | The message is sent normally. |
| 421 | The message is deferred temporarily. because the message is too much and server response is delayed. |
| 450 | It is failed to send the message. there is some relayed smtp server problem or the mailbox is locked. |
| 451 | It is failed to send the message. most likely the receiver problem, not sender problem. |
| 452 | The mail system storage is not enough. |
| 550 | it is rejected by the received mail server |
| 553 | No active user. to address is not exist. |
| 554 | It is failed to send the message. sometimes mail is refused by smtp server or receiver. |
| 2.x.x | Success |
| 4.x.x | Error temporary |
| 5.x.x | Error |
